Observing the Galaxy's massive black hole with gravitational wave bursts

TL;DR

This paper explores how gravitational wave bursts from extreme-mass-ratio events near the Galaxy's black hole can be detected and used to precisely measure the black hole's mass and spin parameters.

Contribution

It provides an analysis of EMRB signals' properties and their potential to constrain the parameters of the Galaxy's massive black hole, including spin and mass.

Findings

EMRBs are detectable for periapse distances less than 65 gravitational radii.

Signals from closer periapses yield more accurate constraints on black hole parameters.

Best cases can determine mass and spin with better than one part in 10^4 accuracy.

Abstract

An extreme-mass-ratio burst (EMRB) is a gravitational wave signal emitted when a compact object passes through periapsis on a highly eccentric orbit about a much more massive object, in our case a stellar mass object about a 10^6 M_sol black hole. EMRBs are a relatively unexplored means of probing the spacetime of massive black holes (MBHs). We conduct an investigation of the properties of EMRBs and how they could allow us to constrain the parameters, such as spin, of the Galaxy's MBH. We find that if an EMRB event occurs in the Galaxy, it should be detectable for periapse distances r_p < 65 r_g for a \mu = 10 M_sol orbiting object, where r_g = GM/c^2 is the gravitational radius. The signal-to-noise ratio scales as \rho ~ -2.7 log(r_p/r_g) + log(\mu/M_sol) + 4.9. For periapses r_p < 10 r_g, EMRBs can be informative, and provide good constraints on both the MBH's mass and spin. Closer orbits provide better constraints, with the best giving accuracies of better than one part in 10^4 for both the mass and spin parameter.